The secret to good propagation predictions is making sure that the inputs to the prediction engine closely reflect the real world. In particular, picking the right antenna parameters for both transmit and receive configurations is key. The normal Station Configuration helps guide the user with pre-configured antennas to help create configurations for typical stations.
An Advanced Station Configuration is available for fine grained control over the antenna specification. This enables you to override the inputs to the prediction engine including the option to upload a custom antenna model which can be generated from antenna modeling software such as EZNEC or HFTA. For HFTA users, we have developed an additional software utility that can generate a full 360 degree model of antennas modeled over real terrain. This utility (called HFTASWEEP) runs under Windows and is available by clicking on the HFTASweep link in the Documentation block at the foot of the site pages.
By using HFTA and HFTASWEEP, you can generate models of your antenna performance at your QTH. Here'a a link to an example that Rick KY6R generated and posted on his blog.
and... as a teaser, here's a graphic that shows the gain by azimuth for his QTH.
Advanced Station Configuration
The Advanced Station Configuration provides finer grained control over antenna parameters than the normal Station Configuration. You create an Advanced Station Configuration in much the same way as a regular Station Configuration - click on the New option under the Navigation Menu and then select Advanced Station Configuration.
The Advanced Station Configuration adds three additional parameters to the antenna specification for EACH band.
The Antenna Gain field allows you to specify the gain of an isotropic radiator. The isotropic radiator is a virtual antenna which has the same gain at all combination of radiation/azimuth angles. Use this option to model a directional antenna of a specific gain for all angles of rotation. For example, if you have a 4-Square for 80m, you could simplify the prediction modeling by using this field with a value of 3 dBi.
Use the Antenna File field to select and upload a VOACAP type 13 antenna file produced by HFTASweep, EZNEC or other antenna modeling software. The site does not check that you are uploading a valid antenna model. The file must have an extension of .txt, .t13 or .13 for the site to accept the upload and the file must be less than 300 KB. If you upload an invalid model, a propagation prediction using this file will simply fail and give you an error message.
Use the Beam Direction field in conjunction with the Antenna File field to set the radiation direction of a modeled directional antenna such as a Yagi.
NOTE: You do not need to use this field with a file generated by HFTASweep. The antenna model file generated by HFTASweep has the radiation pattern for the modeled antenna across ALL azimuth angles.
Using any of these additional fields (Antenna Gain, Antenna File & Beam Direction) will override the choice in the Antenna field (the drop down list of pre-configured antenna types). Specifying anything other than the default value (-100) for Antenna Gain together with the Antenna File/Beam Direction fields will give you results very different from what you expect - SO DONT DO THIS!
If you have special modeling requirements, this form will do the job but you may need some help from Stu K6TU - drop him an email!